Many sickle mechanisms have been previously proposed for agricultural use. However, of numerous designs that have been tried, there are now two major designs in commercial use. In one design, the reciprocating cutting teeth or blades are relatively narrow with edges 30.degree. apart but the stationary guides between them are short and stubby and have exposed points, i.e., unenclosed knife ends. In a second design now in commercial use, the stationary guards are narrow and pointed but are spaced relatively far apart and the cutting edges of the blades diverge at a 60.degree. angle.
In developing the present invention, I have over a period of many years evaluated and tested these and other commercially available sickles with a variety of different kinds of crops from Louisiana to Saskatchewan. During this evaluation, several important shortcomings have become apparent. One major problem is the limitation in cutting capacity, that is to say, the speed at which the implement can be driven through the field and still reliably perform its intended function. Second is the tendency for stems or trash to become jammed in the working parts of the sickle. Third is the tendency for parts to become prematurely worn or broken. Other problems are also significant such as the problems created by the hold-down units that keep the moving blades in place. Some of the previous hold-down units contribute to clogging and thereby limit capacity. Thus, for example, in harvesting wheat with prior equipment, it may be possible to run the implement at a speed of only about 2 miles per hour. However, if conditions become more difficult; for example, if the straw is tough or matted, it is further reduced. In harvesting soybeans when the ground is wet, the stems tend to wedge in the area between the base of the guards, that is to say, adjacent the back ends of the guards where they are attached to the sickle bar, and the speed of the vehicle may have to be decreased to only 1 mile per hour or it may be necessary to stop the implement periodically and clean the sickle by hand. One objective of the invention is to provide an improved sickle which allows increased ground speeds that may reach twice the ground speed permitted by equipment that does not embody the present invention. A further object is to reduce the tendency for stems and other trash to clog and collect in the spaces between the sickle guards, which if able to occur interferes with efficient operation.
Many of the problems associated with prior devices and their limited capacity were found to derive from shortcomings in the geometry and shape of the components. For example, the distance between the guards, it was discovered, was not optimally related to the length of the guards, and the center distance between the guards was not properly related to the width of the throat or channel between the guards. Furthermore, the cutting angle between each tooth and the side edge of the guard with which it cooperates was not properly selected to cooperate efficiently with the channel dimensions.
In view of these and other deficiencies of the prior art, it is a major objective of the invention to provide an improved sickle for agricultural use wherein improvements in the relative placement and geometry of the several parts cooperate together to improve performance and particularly the cutting capacity so that ground speeds can be doubled or more than doubled in some cases while, at the same time, reducing the amount of clogging that takes place without a sacrifice in product life or the requirement for replacement of worn parts.
These and other more detailed and specific objects of the invention will become apparent in view of the accompanying description which sets forth the invention by way of example.